The present invention generally relates to a waterproof construction of a wiring harness having a splice portion at a water immersion area where water immersion is likely to take place in a motor vehicle and more particularly, to a waterproof construction of a wiring harness, in which the position of the splice portion is improved so as to prevent penetration of water into the wiring harness from the splice portion.
As shown in FIG. 1, a motor vehicle is divided into a cabin side X and an engine side Y and a wiring harness W/H provided between the cabin side X and the engine side Y is mounted, through a grommet 2, in a through-hole of a partition wall 1 between the cabin side X and the engine side Y. A main line W/H-1 of the wiring harness W/H is provided so as to extend from a space S1 above each of wheel wells 3 disposed at opposite sides of an engine compartment ER to a space S2 above a radiator support 4 disposed in front of the engine compartment ER. Meanwhile, branch lines W/H-2 branching off from the main line W/H-1 are chiefly carried into the engine compartment ER via through-holes formed on an outer wall 5 of the engine compartment ER so as to be connected to connectors C1 and C2 disposed in the engine compartment ER and a portion of the branch lines W/H-2 is connected to a waterproof connector C3 disposed outside the engine compartment ER.
In a wiring route of the wiring harness W/H, the space S1 above each of the wheel wells 3 disposed at the opposite sides of the engine room ER and the space S2 above the radiator support 4 disposed in front of the engine room ER are water immersion areas where water immersion is likely to take place, as shown by the hatchings in FIG. 1.
In the above mentioned known wiring harness W/H, in case opposite ends of a wire D1 of the branch line are connected to the connectors C1 and C2 disposed in the engine compartment ER and one end of a wire D2 of the branch line is connected to the connector C3 disposed outside the engine compartment ER such that the wires D1 and D2 are connected to each other by splicing as shown in FIG. 2, its splice portion P of the branch line is disposed in the water immersion area.
In case water penetrates, through a tape wound around an outer periphery of the wiring harness, into the wiring harness in which a group of wires having the splice portion referred to above are bundled and protected, water which has penetrated into the wiring harness is sucked by the splice portion P and is drawn into the connectors C1 to C3 through gaps among the wires, thereby resulting in defective connections or short-circuiting.
In order to solve this problem, a U-shaped portion D1'-1 extending up to the cabin side X in a water nonimmersion area may be provided, through a grommet (not shown), on a wire D1' having opposite ends connected to the connectors C1 and C2, respectively so as to be spliced with a wire D2' connected to the connector C3 such that a splice portion P' of the wires D1' and D2' is formed as shown in FIG. 3. If the known wiring harness is assembled in the water nonimmersion area as shown in FIG. 3 when the splice portion P' of the wires D1' and D2' is bundled with the remaining wires, no problem arises. However, as shown in FIG. 4, such a case may happen in which the wiring harness is assembled in a state where the splice portion P' of the wires D1' and D2' is bundled with the remaining wires in the water immersion area.
In the above described known method in which the U-shaped portion P' is provided on the wire D1' having the opposite ends connected to the connector C1 and C2 so as to be spliced with the wire D2' having one end connected to the connector C3, the position of the U-shaped portion D1'-1 is not regulated. Therefore, such a drawback is incurred that during assembly steps of the wiring harness, the wiring harness should be assembled by paying close attention to direction of the U-shaped portion D1'-1.